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Commit 4102b533 authored by Vineet Gupta's avatar Vineet Gupta
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ARC: [mm] Aliasing VIPT dcache support 2/4 



This is the meat of the series which prevents any dcache alias creation
by always keeping the U and K mapping of a page congruent.
If a mapping already exists, and other tries to access the page, prev
one is flushed to physical page (wback+inv)

Essentially flush_dcache_page()/copy_user_highpage() create K-mapping
of a page, but try to defer flushing, unless U-mapping exist.
When page is actually mapped to userspace, update_mmu_cache() flushes
the K-mapping (in certain cases this can be optimised out)

Additonally flush_cache_mm(), flush_cache_range(), flush_cache_page()
handle the puring of stale userspace mappings on exit/munmap...

flush_anon_page() handles the existing U-mapping for anon page before
kernel reads it via the GUP path.

Note that while not complete, this is enough to boot a simple
dynamically linked Busybox based rootfs

Signed-off-by: default avatarVineet Gupta <vgupta@synopsys.com>
parent 6ec18a81

arch/arc/Kconfig

+4 −0
Original line number Diff line number Diff line
@@ -182,6 +182,10 @@ config ARC_CACHE_PAGES 
	  Note that Global I/D ENABLE + Per Page DISABLE works but corollary

	  Global DISABLE + Per Page ENABLE won't work



config ARC_CACHE_VIPT_ALIASING

	bool "Support VIPT Aliasing D$"

	default n



endif	#ARC_CACHE



config ARC_HAS_ICCM

arch/arc/include/asm/cacheflush.h

+45 −8
Original line number Diff line number Diff line
@@ -50,18 +50,55 @@ void dma_cache_wback(unsigned long start, unsigned long sz); 
#define flush_cache_vmap(start, end)		flush_cache_all()

#define flush_cache_vunmap(start, end)		flush_cache_all()



/*

 * VM callbacks when entire/range of user-space V-P mappings are

 * torn-down/get-invalidated

 *

 * Currently we don't support D$ aliasing configs for our VIPT caches

 * NOPS for VIPT Cache with non-aliasing D$ configurations only

 */

#define flush_cache_dup_mm(mm)			/* called on fork */

#define flush_cache_dup_mm(mm)			/* called on fork (VIVT only) */



#ifndef CONFIG_ARC_CACHE_VIPT_ALIASING



#define flush_cache_mm(mm)			/* called on munmap/exit */

#define flush_cache_range(mm, u_vstart, u_vend)

#define flush_cache_page(vma, u_vaddr, pfn)	/* PF handling/COW-break */



#else	/* VIPT aliasing dcache */



/* To clear out stale userspace mappings */

void flush_cache_mm(struct mm_struct *mm);

void flush_cache_range(struct vm_area_struct *vma,

	unsigned long start,unsigned long end);

void flush_cache_page(struct vm_area_struct *vma,

	unsigned long user_addr, unsigned long page);



/*

 * To make sure that userspace mapping is flushed to memory before

 * get_user_pages() uses a kernel mapping to access the page

 */

#define ARCH_HAS_FLUSH_ANON_PAGE

void flush_anon_page(struct vm_area_struct *vma,

	struct page *page, unsigned long u_vaddr);



#endif	/* CONFIG_ARC_CACHE_VIPT_ALIASING */



/*

 * Simple wrapper over config option

 * Bootup code ensures that hardware matches kernel configuration

 */

static inline int cache_is_vipt_aliasing(void)

{

#ifdef CONFIG_ARC_CACHE_VIPT_ALIASING

	return 1;

#else

	return 0;

#endif

}



#define CACHE_COLOR(addr)	(((unsigned long)(addr) >> (PAGE_SHIFT)) & 3)



/*

 * checks if two addresses (after page aligning) index into same cache set

 */

#define addr_not_cache_congruent(addr1, addr2)				\

	cache_is_vipt_aliasing() ? 					\

		(CACHE_COLOR(addr1) != CACHE_COLOR(addr2)) : 0		\



#define copy_to_user_page(vma, page, vaddr, dst, src, len)		\

do {									\

	memcpy(dst, src, len);						\

arch/arc/include/asm/page.h

+15 −1
Original line number Diff line number Diff line
@@ -16,13 +16,27 @@ 
#define get_user_page(vaddr)		__get_free_page(GFP_KERNEL)

#define free_user_page(page, addr)	free_page(addr)



/* TBD: for now don't worry about VIPT D$ aliasing */

#define clear_page(paddr)		memset((paddr), 0, PAGE_SIZE)

#define copy_page(to, from)		memcpy((to), (from), PAGE_SIZE)



#ifndef CONFIG_ARC_CACHE_VIPT_ALIASING



#define clear_user_page(addr, vaddr, pg)	clear_page(addr)

#define copy_user_page(vto, vfrom, vaddr, pg)	copy_page(vto, vfrom)



#else	/* VIPT aliasing dcache */



struct vm_area_struct;

struct page;



#define __HAVE_ARCH_COPY_USER_HIGHPAGE



void copy_user_highpage(struct page *to, struct page *from,

			unsigned long u_vaddr, struct vm_area_struct *vma);

void clear_user_page(void *to, unsigned long u_vaddr, struct page *page);



#endif	/* CONFIG_ARC_CACHE_VIPT_ALIASING */



#undef STRICT_MM_TYPECHECKS



#ifdef STRICT_MM_TYPECHECKS

arch/arc/include/asm/tlb.h

+9 −2
Original line number Diff line number Diff line
@@ -30,13 +30,20 @@ do { \ 
/*

 * This pair is called at time of munmap/exit to flush cache and TLB entries

 * for mappings being torn down.

 * 1) cache-flush part -implemented via tlb_start_vma( ) can be NOP (for now)

 *    as we don't support aliasing configs in our VIPT D$.

 * 1) cache-flush part -implemented via tlb_start_vma( ) for VIPT aliasing D$

 * 2) tlb-flush part - implemted via tlb_end_vma( ) flushes the TLB range

 *

 * Note, read http://lkml.org/lkml/2004/1/15/6

 */

#ifndef CONFIG_ARC_CACHE_VIPT_ALIASING

#define tlb_start_vma(tlb, vma)

#else

#define tlb_start_vma(tlb, vma)						\

do {									\

	if (!tlb->fullmm)						\

		flush_cache_range(vma, vma->vm_start, vma->vm_end);	\

} while(0)

#endif



#define tlb_end_vma(tlb, vma)						\

do {									\

arch/arc/mm/cache_arc700.c

+129 −5
Original line number Diff line number Diff line
@@ -68,6 +68,7 @@ 
#include <linux/mmu_context.h>

#include <linux/syscalls.h>

#include <linux/uaccess.h>

#include <linux/pagemap.h>

#include <asm/cacheflush.h>

#include <asm/cachectl.h>

#include <asm/setup.h>
@@ -138,6 +139,7 @@ void __cpuinit arc_cache_init(void) 
	struct cpuinfo_arc_cache *ic = &cpuinfo_arc700[cpu].icache;

	struct cpuinfo_arc_cache *dc = &cpuinfo_arc700[cpu].dcache;

	int way_pg_ratio = way_pg_ratio;

	int dcache_does_alias;

	char str[256];



	printk(arc_cache_mumbojumbo(0, str, sizeof(str)));
@@ -184,9 +186,13 @@ void __cpuinit arc_cache_init(void) 
		panic("Cache H/W doesn't match kernel Config");

	}



	dcache_does_alias = (dc->sz / ARC_DCACHE_WAYS) > PAGE_SIZE;



	/* check for D-Cache aliasing */

	if ((dc->sz / ARC_DCACHE_WAYS) > PAGE_SIZE)

		panic("D$ aliasing not handled right now\n");

	if (dcache_does_alias && !cache_is_vipt_aliasing())

		panic("Enable CONFIG_ARC_CACHE_VIPT_ALIASING\n");

	else if (!dcache_does_alias && cache_is_vipt_aliasing())

		panic("Don't need CONFIG_ARC_CACHE_VIPT_ALIASING\n");

#endif



	/* Set the default Invalidate Mode to "simpy discard dirty lines"
@@ -312,7 +318,7 @@ static inline void __dc_line_loop(unsigned long paddr, unsigned long vaddr, 
	}

}



/* For kernel mappings cache op index is same as paddr */

/* For kernel mappings cache operation: index is same as paddr */

#define __dc_line_op_k(p, sz, op)	__dc_line_op(p, p, sz, op)



/*
@@ -464,10 +470,47 @@ static void __ic_line_inv_vaddr(unsigned long paddr, unsigned long vaddr, 
 * Exported APIs

 */



/*

 * Handle cache congruency of kernel and userspace mappings of page when kernel

 * writes-to/reads-from

 *

 * The idea is to defer flushing of kernel mapping after a WRITE, possible if:

 *  -dcache is NOT aliasing, hence any U/K-mappings of page are congruent

 *  -U-mapping doesn't exist yet for page (finalised in update_mmu_cache)

 *  -In SMP, if hardware caches are coherent

 *

 * There's a corollary case, where kernel READs from a userspace mapped page.

 * If the U-mapping is not congruent to to K-mapping, former needs flushing.

 */

void flush_dcache_page(struct page *page)

{

	/* Make a note that dcache is not yet flushed for this page */

	struct address_space *mapping;



	if (!cache_is_vipt_aliasing()) {

		set_bit(PG_arch_1, &page->flags);

		return;

	}



	/* don't handle anon pages here */

	mapping = page_mapping(page);

	if (!mapping)

		return;



	/*

	 * pagecache page, file not yet mapped to userspace

	 * Make a note that K-mapping is dirty

	 */

	if (!mapping_mapped(mapping)) {

		set_bit(PG_arch_1, &page->flags);

	} else if (page_mapped(page)) {



		/* kernel reading from page with U-mapping */

		void *paddr = page_address(page);

		unsigned long vaddr = page->index << PAGE_CACHE_SHIFT;



		if (addr_not_cache_congruent(paddr, vaddr))

			__flush_dcache_page(paddr, vaddr);

	}

}

EXPORT_SYMBOL(flush_dcache_page);
@@ -612,6 +655,87 @@ noinline void flush_cache_all(void) 


}



#ifdef CONFIG_ARC_CACHE_VIPT_ALIASING



void flush_cache_mm(struct mm_struct *mm)

{

	flush_cache_all();

}



void flush_cache_page(struct vm_area_struct *vma, unsigned long u_vaddr,

		      unsigned long pfn)

{

	unsigned int paddr = pfn << PAGE_SHIFT;



	__sync_icache_dcache(paddr, u_vaddr, PAGE_SIZE);

}



void flush_cache_range(struct vm_area_struct *vma, unsigned long start,

		       unsigned long end)

{

	flush_cache_all();

}



void copy_user_highpage(struct page *to, struct page *from,

	unsigned long u_vaddr, struct vm_area_struct *vma)

{

	void *kfrom = page_address(from);

	void *kto = page_address(to);

	int clean_src_k_mappings = 0;



	/*

	 * If SRC page was already mapped in userspace AND it's U-mapping is

	 * not congruent with K-mapping, sync former to physical page so that

	 * K-mapping in memcpy below, sees the right data

	 *

	 * Note that while @u_vaddr refers to DST page's userspace vaddr, it is

	 * equally valid for SRC page as well

	 */

	if (page_mapped(from) && addr_not_cache_congruent(kfrom, u_vaddr)) {

		__flush_dcache_page(kfrom, u_vaddr);

		clean_src_k_mappings = 1;

	}



	copy_page(kto, kfrom);



	/*

	 * Mark DST page K-mapping as dirty for a later finalization by

	 * update_mmu_cache(). Although the finalization could have been done

	 * here as well (given that both vaddr/paddr are available).

	 * But update_mmu_cache() already has code to do that for other

	 * non copied user pages (e.g. read faults which wire in pagecache page

	 * directly).

	 */

	set_bit(PG_arch_1, &to->flags);



	/*

	 * if SRC was already usermapped and non-congruent to kernel mapping

	 * sync the kernel mapping back to physical page

	 */

	if (clean_src_k_mappings) {

		__flush_dcache_page(kfrom, kfrom);

	} else {

		set_bit(PG_arch_1, &from->flags);

	}

}



void clear_user_page(void *to, unsigned long u_vaddr, struct page *page)

{

	clear_page(to);

	set_bit(PG_arch_1, &page->flags);

}



void flush_anon_page(struct vm_area_struct *vma, struct page *page,

		     unsigned long u_vaddr)

{

	/* TBD: do we really need to clear the kernel mapping */

	__flush_dcache_page(page_address(page), u_vaddr);

	__flush_dcache_page(page_address(page), page_address(page));



}



#endif



/**********************************************************************

 * Explicit Cache flush request from user space via syscall

 * Needed for JITs which generate code on the fly